1. Field of the Invention
The present invention relates generally to a heat-shrinking film packaging machine, and in particular to a device for controlling flow rate of hot air that heats and thus shrinking a plastic film for packaging articles.
2. The Related Art
Heat-shrinking plastic films have been widely used to wrap and pack consumer products, such as foods, books, video/audio compact disks for protecting the products from contamination and damage. A packaging machine is required to wrap the package film around the product and supply hot air flow to heat the plastic film in order to have the film shrink and thus securely wrap around an article to be packaged.
Since the articles or goods to be packaged with heat-shrinking films may have size and configuration significantly varied from each other. This makes uniformly heating the film surrounding the articles very difficult because while a portion of the film gets overheated and thus over-shrunk, the remaining portion of the film is still under-heated and thus under-shrunk. This leads to poor quality of packaging.
Thus, it is desired to have a device for controlling heat applying to the film in order to overcome the above problems.
An object of the present invention is to provide a hot air flow control device for a heat-shrinking film packaging machine that controls the flow rate of hot air supplied to different portions of an article packaged by a heat-shrinking plastic film so as to provide proper amount of heat to every portion of the film for high quality packaging.
Another object of the present invention is to provide a hot air flow supply device having exit ports for guiding hot air flow towards an article wrapped by a heat-shrinking film, the exit ports being selectively and partially blocked to control flow rate of the hot air through the ports.
To achieve the above objects, in accordance with the present invention, there is provided a hot air flow control device incorporated in a heat-shrinking film packaging machine for controlling the flow rate of hot air that is supplied to an article to be packaged to have a heat-shrinking film surrounding the article heated and shrunk and thus tightly packaging the article. The hot air flow control device comprises two air supply devices located on opposite sides of a conveyor that conveys the article through a channel defined by the air supply devices. Each air supply device has a surface in which an array of openings is defined and arranged in rows and columns for supplying hot air toward the article. A blocking bar is movably mounted to the surface of each air supply device and associated with each row of the openings. The blocking bar is movable with respect to the openings to selectively and partially block the openings for controlling hot air flow through the openings. Positioning pins are formed on the surface of each air supply device and are movably received in elongate slots defined in the blocking bar for guiding the movement of the blocking bar with respect to the surface of the air supply device. Driving holes are defined in the blocking bar for manually or automatically moving the blocking bar with respect to the openings of the air supply device.